Pyrolysis of lignin in the gas-phase using “wall-less” and cw-IR CO₂ laser powered homogeneous pyrolysis (LPHP) non-isothermal and continuous droplet evaporation (CDE) isothermal reactors has been performed. Hydrolytic lignin was dissolved in an acetone/water (9:1) mixture and dispersed into LPHP and CDE reactors using a constant output atomizing device and a syringe pump, respectively. Large differences in gas phase depolymerization of lignin have been seen in both reactors. The temperature distribution in the LPHP reactor was evaluated by thermocouple measurements and validated by the method of “chemical thermometer” and COMSOL Multiphysics simulations. The gas phase delivery of lignin into the hot zone of the LPHP reactor under “wall-less” conditions led to the breakdown of lignin into paramagnetic fragments that deposited onto the cell walls, which were studied by electron paramagnetic resonance spectroscopy. Phenolics were not detected at all in the LPHP reactor. However, major phenolics (phenol(s), guaiacol(s), syringol(s)) were detected in the CDE reactor. At laser powers higher than 20 W and a high initial concentration of dispersed lignin (5 g/L), an intensification of demethoxylation reactions of phenolics by concomitant alkylation of aromatic rings along with the expulsion of CO from phenoxy rings (to account for formation of indenes and naphtalenes) was achieved in the LPHP reactor when a prepyrolyzed mixture from the CDE reactor entered the LPHP reactor. The yields of qualified biofuel products such as styrene, different alkyl benzenes, and surrogate fuels of diesel such as indene, 1,2-dihydro naphthalene, naphthalene, and other derivatives were detected in the LPHP reactor with decreasing amounts of phenolics. These results represent valuable observations about the primary mechanism of lignin depolymerization.

中文翻译：

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气相等温和cw-CO ₂激光驱动非等温反应器中木质素的热解

使用“无壁”和cw-IR CO ₂在气相中热解木质素已经进行了激光驱动的均相热解（LPHP）非等温和连续液滴蒸发（CDE）等温反应器。将水解木质素溶解在丙酮/水（9：1）混合物中，并分别使用恒定输出雾化装置和注射泵分散到LPHP和CDE反应器中。在两个反应器中都发现木质素在气相解聚中的巨大差异。通过热电偶测量评估了LPHP反应器中的温度分布，并通过“化学温度计”和COMSOL Multiphysics模拟方法对其进行了验证。在“无壁”条件下将木质素气相输送到LPHP反应器的热区导致木质素分解为顺磁性碎片，并沉积在细胞壁上，这已通过电子顺磁共振波谱进行了研究。在LPHP反应器中根本未检测到酚类。但是，在CDE反应器中检测到了主要的酚类（酚，愈创木酚，丁香酚）。在高于20 W的激光功率和较高的分散木质素初始浓度（5 g / L）下，伴随芳香环的烷基化以及苯氧基环上的CO的排出，酚类化合物的脱甲氧基化反应加剧。当来自CDE反应器的预热解混合物进入LPHP反应器时，在LPHP反应器中就达到了Indenses和Naphtalenes）。在LPHP反应器中，随着酚类含量的减少，检测到了合格的生物燃料产品（例如苯乙烯，不同的烷基苯）和柴油的替代燃料（例如茚，1,2-二氢萘，萘和其他衍生物）的产率。